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    Spring Allegedly Arrives Thursday

    3/18/2014, 8:33:23 AM

    Monday, 11:55 a.m.

    Three days and counting! We're almost to spring officially! However, tell that to the folks living across Virginia and West Virginia into Maryland, Delaware, southernmost Pennsylvania and the southern half of New Jersey. Some locations outside of Washington, D.C., picked up nearly a foot of snow overnight and early this morning, an amazing accomplishment given the fact the normal high is 55 at Dulles Airport today! All I know is that my time visiting our radio client WCOA in Pensacola, Fla., was wonderfully mild, even being in the 60s and below average for them, when you compare it to the chill of central Pennsylvania this morning!

    Before I go into the specifics of the pattern for the rest of the month, let me broad brush it by saying winter is not going away without a fight. That may not necessarily mean a lot of snow in places that wouldn't normally see it in late March, but it does mean persistently being much below normal, especially from the northern Plains and Midwest to the East Coast. Let me show you three charts. The first of these is the 6z March 17 GFS ensemble seven-day means for tomorrow through next Monday:

    The next chart is from the same model run, only for the period March 24 to 30:

    Lastly, the Canadian NAEFS model for the same time period:

    Where is the warmth from the eastern Plains to the East Coast, especially from the Dakotas and Midwest to the Northeast and mid-Atlantic? There isn't any. Oh, there will be a couple of short warmups, as there usually are in any persistently cold pattern. One of them will be later this week, and there will be another one later next week. However, the warm periods will be two to at most three days, and you'll only see temperatures sneaking above average for a day or at most two. The colder-than-average days will easily outweigh the normal to above-normal days combined, and the magnitude of those negative departures will dwarf the meager positive ones.

    What makes this more amazing is that the Atlantic really has had nothing to do with this. Look at the North Atlantic Oscillation (NAO) since the latter half of November:

    It's mainly been positive, so there's been no blocking. Instead, the Pacific has held all the cards this winter, with the dominant pattern of a ridge poking up in the eastern Pacific all the way into Alaska, and a deep trough downstream over eastern North America, often highlighted by a close low, or 'polar vortex' over Ontario and Quebec, if not farther south. Even though the pattern has been a progressive one, with the most intense shots of cold lasting just a couple of days, there's almost always been something else to come right in and replace what's departing or moderating. That looks to be the case for the next two weeks.

    In the short term, today's storm is winding down, at least in terms of accumulating snows in the mid-Atlantic. It's not over in the Southeast, as an upper-level trough still has to slide slowly across the area this afternoon and tonight. That means more rain, and quite a bit of it, over northern and central Florida, Georgia and parts of South Carolina. The 12z March 17 NAM 24-hour precipitation forecast through tomorrow morning:

    High pressure over upstate New York and New England will keep the interior Northeast cold and dry through tomorrow, but the clockwise flow around the high will mean a persistent onshore flow in the mid-Atlantic, which means a lot of clouds and a very slow recovery to normal later in the week. In fact, the danger across Virginia and Maryland into Delaware late tonight and tomorrow is that the air mass moistens to the point where drizzle breaks out, and if that happens with temperatures still below the freezing mark, there could be a lot of icing issues to worry about late tonight into tomorrow morning. That could be an issue Wednesday morning in parts of Pennsylvania as well.

    The next storm will roll through the Rockies this afternoon and redevelop over Nebraska tonight. Snow will spread from Wyoming into parts of South Dakota and Nebraska tonight into tomorrow. After some light mixed precipitation in the Midwest this afternoon and tonight, the air will turn cold enough to support mainly snow tomorrow into tomorrow night as the storm rolls eastward. That said, southern Wisconsin and points south will end up with mostly rain from that same storm, and, at that, not much rain.

    With the storm curling up into northern Michigan Wednesday, milder air will get pulled into the Ohio Valley ahead of a cold front. As the low-level cold, dense air east of the Appalachians gets mixed out behind this front on Thursday, look for temperatures to rebound to near normal.

    The air behind this storm isn't terribly cold. The surface high behind it builds through the southern Plains into the Southeast, not out of the remote frozen hinterlands of northern Canada, so the air mass sweeping across the Plains and Mississippi Valley will be much more Pacific in nature. That means warming for the Ohio and Tennessee valleys Thursday and especially Friday and into the East Friday and Saturday ahead of the next cold front. And trust me, there will be another one!

    That front, according to the 0z GFS, would reach the East Coast late Saturday:

    This system probably produces snow from the Great Lakes to upstate New York and interior New England. If you look at that map closely, you will also note the next high moving toward the Dakotas, and that means another surge of arctic air pouring in behind the storm and its attendant cold front. So, instead of a mild first weekend of spring, it looks to be much colder than average from the northern Rockies and northern and central Plains to the Great Lakes and Ohio Valley, with the cold air reaching the East Saturday night and Sunday.

    After a few days of that kind of cold, it looks to moderate again later next week, only for optimism of springtime warmth to be turned around into another depths-of-winter cold air mass the following weekend.

    Yes, Pensacola is looking even better right about now!!!

    The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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